The present invention relates to radio communications and, more particularly, to a distributed wideband architecture for use in radio communications systems.
Today, indoor cellular systems, as well as many small-cell, or pico-cell, outdoor systems, use relatively unintelligent, centralized base stations in conjunction with distributed analog transceivers to transmit and receive communication signals to and from local mobile users operating within the systems. Communication signals are allocated to, and modulated on, frequency division multiplexed (FDM) carriers, or channels, within an overall frequency bandwidth designated for use by the systems. Channel selection and allocation is typically performed using relatively costly, narrowband analog filters located within the analog transceivers or within the base station. The analog filters are tuned to a pre-selected and fixed frequency bandwidth and are capable of supporting only a single air-interface standard. Thus, current systems are inflexible in terms of protocol and, for a given number of transceivers, are limited with respect to the overall number of users which can be simultaneously accommodated in an overall geographic coverage area.
The inflexible nature of current system design also yields fixed user capacity within each single-transceiver coverage area and makes extremely inefficient use of transceiver hardware. As a result, available FDM channels may lie dormant even as potential users are denied access to the system. Empirical data suggest that usage efficiency in these systems is typically less than 30%. Such inefficiency often requires that a large number of analog transceivers be used to obtain only modest system capacity and sometimes leads to overly complex and overly costly base station design. Also, due to the fixed-protocol nature of current systems, system designers must practice careful pre-installation frequency planning and coordination with respect to existing, comparatively powerful, outdoor systems. This can result in high installation and operations costs and may further limit the capacity of the installed system. Thus, there is a real need for an improved radio system architecture.